Production of liquid polymers



Dec. 31, 940. 'E J, HouDRY PRODUCTION'OF LIQUID POLYMERS Filed Nov. 23, 193e xNvENToR EENE J;Huu dY| ATTORNEY Eu a 26E. hmm n .m5 .3

Patented Dec. 31, 1940 I UNITED STATES- PATENT' OFFICE' rnonUC'rIoN oF LIQUID roLYMEns Eugenel J. Houdry, Haverford, Pa., assigner to Hendry Process Corporation, Wilmington, Del., a corporation of Delaware Application November 23, 1936, Serial No. 112,381

6 Clims- (CL 196-10) carbon gases. Another object is to act upon aA given charge of hydrocarbon gases so as toconvert and extract therefrom as liquid a major portion of unsaturates contained therein. Another object is to effect dehydrogenation of gaseous material to convert at least a part of the same l5 into unsaturates capable of polymerization. An-

other object is to devise an yimproved circuit comprising both polymerization and dehydrogenation zones for effecting the above objects. Still other objects will be apparent from the detailed description which follows. y

In order to illustrate the invention and the manner of its operation a preferred embodiment thereof is illustrated in the accompanying drawing which shows diagrammatically a circuit involving polymerization and dehydrogenation and indicates the requisite pieces oi apparatus.

Referring to the drawing, a charge of hydrocarbon gases containingv substantial amounts of unsaturates from any source is fed by line I a0 through heater 2 and is then sent under reaction conditions into a primary polymerization zone which may comprise one converter or a battery of converters 3 (two being shown). Polymerized and unpolymerized materials leave the mue by 35 line 4, pass through unit 5 where they are either heated or cooled, as may be necessary, for the subsequent separation oi liquidpolymers which takes place in fractionator 6. The liquid products are removed by line 1, a reboiling circuit 8 being utilized at the bottom of fractionator 6 if desired, while the gaseous overhead products pass by line 9 through condenser` i0 into a separator li which may have a vent l2 for the removal of uncondensed material. A. part' of the liquefied material in separator l I may be pumped back into fractionator I by line'il to act as re'- iiux. The remainder is sent by line I4 throughunit l5 and under reaction conditions into a second polymerization zone which may comprise 59 a battery of converters I6. The stream of mal terial leaving this zone by line I1 may all be sent back by line I8 to be added to the stream of products in line l, leaving therst polymerization zone-'for recirculation through fractlonator I and the second polymerization zone, or all of it may pass through heating or cooling unit I9 into fractionator 2li. By preference the stream in line I1 is divided, a portion being recirculated through line I8 while the remainder passes into fractionator 20. The liquid Polymers leave the last- I named element by line 2l, a reboiling circuit inf dicated 'at 22 being utilized if desired, and the overhead gaseous material leaves fractionator 20 by line 23. A part of the overhead may be sent through condenser '24 into separator 25, which 101 has a v ent 26, and provides liquid retluxed material which is pumped back into the top of fractionator 20 by line 21. The remainder of this overhead, which is practically stripped of all unsaturates and which may be augmented.' by the 15 gaseous material vented through lines l2 and 28, is sent by line 28 through heat exchanger 29 and heater 30 under reaction conditions into a dehvdrogenationA zone wherein the hydrocarbon saturates are cracked and converted at least par- 20 tially into unsaturates. To line 28 additional charge comprising gaseous hydrocarbons poor in unsaturates may be added by line la. 'Ihe dehydrogenation may be effected in one or more converters 3|. The products leave the dehydro- 25 'genation zone by line 32 which conducts them back through the heat exchanger 29, thence through condenser 33 where the material is cooled, put under pressure by pump 34, sent through cooler or condenser 35 and then into a 30 separator 36 whence hydrogen and other light gases are removed by line 31 for fuel or other uses while the liquefied material, including unsaturates, is sent through line 38 to line l where it is added -to fresh charge entering the circuit. 35 When the material available for charge comprises essentially saturated hydrocarbons, as in natural gas, theentrance to the circuit will be by line l a rather than by line i.

The polymerization of unsaturates in the two 40 zones provided for this purpose may be eiected l in any known 4or desired manner, either thermally or catalytically, either in gaseous phase or in liq-` uid phaseor ina combination of both phases. 'I'he ratio oi recycled materialI to unrecycled- 45 charge going to the iirst fractionator 'l `may range from 0.5:1 to 5:1. The usual ratio is about lVzzl. likewise the -dehydrogenation oi' the tail 1 gases from the second polymerization zone and of any fresh material added by line la to produce 50 unsaturates may be effected in any known manner either thermally or catalytically. Sumcient apparatus is` indicated in the circuit to permit 'thesame to useany necessary temperature, pressure and rate of feed. The polymerization effected in one of the two polymerization zones may be different from that carried out in the other, the general purpose being to produce a maximum yield of the desired type of liquid polymers.

One method of polymerization which is found to be quite suitable for both the primary and the second polymerization zones is a catalytic operation eilected at low temperature (below the critical temperature of the charge) and in liquid phase in contact vwith catalyst which can be readily restored to activity through regenerating by oxidation either in situ or after removal from the converter. The preferred catalyst is silicious in nature and preferably a blend of silica and alumina. in controlled ratio. It may be produced by chemical treatment of naturally occurring clays or synthetically as a type of gel in known manner. A good catalyst is one producedby the interaction of a soluble silicate and a soluble alum to provide a silica to alumina weight ratio of about 9:1, this material being prepared in the form of grains or molded pieces. 'I'he operation takes place within the range of 50 to 300 F., the highest yield of light or high boiling hydrocarbons in the gasoline range being made at a temperature of 180 to 225 F. The charge is sent to .the zone wholly or partly in liquid phase and is maintained under suiileient pressure in the polymerization zone so that at least one constituent is always in liquid phase. The pressure used depends somewhat upon the temperature selected but may range up to 700 lbs. per sq. in. ibi' the preferential operating range of 180 to 225 F. to produce gasoline, pressure of about 500 pounds is normally used. The feed rate to the polymerization zone may be from 5 to 'l5 cu. ft. oi' gas per hour per liter of catalyst, depending upon the amount of unsaturates in the charge. When the charge contains about of unsaturates, a good rate is 25 cu. ft. of gas per hour per liter of catalyst. 'Ihe feed rate would be increased as the percentage of unsaturates decreases. In general, by operating the zone at constant temperatures, the yield of polymers in the gasoline boiling range can be increased by increasing the rate of feed. On the other hand. by operating at constant feed rate the production of polymers higher boiling than gasoline can be increased by raising the temperature. This liquid phase process of polymerization is disclosed vand claimed in the co-v pending application of myself and J. P. Daugherty, Jr., Serial No. 239,632, illed November 9,

1938. as a substitute for and a` continuation-inpart of- Serial No. 109,680, iiled November 7, 1936.

By using the particular polymerization process described above, it is possible to convert from 4,0 to 50% of the unsaturates in the charge into recoverable liquids in each of the polymerization zones. Asood operation `is to use the same reaction conditions in both zones. for example, 220 P. and 450 pounds pressure.V Another operation which gives a slightly -better yield is to use one set of operating conditions. as 200 l". and 400 pounds pressure, inthe primary polymerization lone and higher temperature and 'pressure conditiorisv inthe second vpolymerization zone with a recirculating feed ratio in the second zone of about 2:1. Either of these operations leaves only e small relativel percentage of unsaturstes in the overhead material from fractionator 20 which is sent to the dehydrogenating sone.

A good operation for the dehydrogenation zone is one effected catalytieally at low pressure and in vapor phase. -The catalyst is preferably a azzecca blend of chromium oxide and aluminum oxide on 'facilitate regeneration. Alumina. in conjunction with chromium oxide, acts as a stabilizer giving optimum yields over a broader range of temperature with a minimum of undesirable side reactions. The operating temperature is in the range of 900 to i000 F. and preferentially in the range 4of 925 to 975 F. The pressure is kept as low as possible, usually below pounds per sq. in. The charge is'sent in vapor phase at la rate of the order of 6 to l5 volumes of gas per minute per volume of catalyst, giving acontact time up to approximately 10 seconds. The longer contact time is utilized for the lower temperature in the operating range; for a temperature of 975 F. the contact time is usually 6 seconds or less. The percentage of conversion to unsaturates is usually from 17 to 21% per volume of outlet gases or from 22 to 26% by weight of saturates transformed. By preference, the catalyst is disposed in a deep bed with perforated inlet and outlet conduits symmetrically arranged and embedded in the mass to effect parallel flow of reactants and uniform operating conditions throughout the converter, after the manner disclosed in my United States Patent No. 2,042,468 issued June 2, 1936.

The hydrogen produced during the cracking operation in the dehydrogenation zone can be recirculated backA through the polymerization zones since it has little if any adverse eilect upon `the polymerizing operation. especially when conducted in the liquid phase as set forth above. However, its volume steadily increases as the operation continues, and hence it is advisable'to remove it from the system as provided by separater 88 which is interposed between the dehydrogenation zone and the point of addition to the charge in line I ofthe unsaturates produced inthe last mentioned zone.

While the invention is hereindisclosed in what is now considered to be a preferable form, it is to be understood that the invention is not limited to the specific details thereof but covers all changes, modiiications and adaptations within the scope of theappen'ded claims.

I claim as my invention:

1. Process of treating hydrocarbon gases to effect polymerization and the recovery of desirablev liquid products comprising sendingI fresh charge -under reaction conditions to a primary polymerization zone, removing liquid polymers from the stream leaving said zone, sending the remainder of the stream under reaction conditions to a second polymerization zone, adding at least a part of the products of'said last named zone to the stream leaving the primary polymerization zone for removal o'f liquid polymers and for recirculation of unremoved material through said second polymerization zone, effecting a final removal of liquid polymers after said cracking zone to convert the same at least partly into ,unsaturated and-adding the unsaturates se remainder of the stream under reaction conditions to a second polymerization zone, dividing the stream leaving said second polymerization zone and adding a part to the stream leaving the primary polymerization zone for further treatment in the second polymerization zone, removing liquid polymers from the remainder of the stream leaving said second polymerization zone, sending the gases from thelast-removing step under reaction conditions to a dehydrogenation or gas cracking zone to convert the same at least partly into unsaturates. sending the resulting unsaturates back to said primary polymerization zone, and repeating the above steps.

3. Process of treating low boiling, normally under sufficient preure to maintain the charge in liquid phase, recycling fluid products from one of said zones, which is subsequent to the first.

zone of said serially arranged plurality, back into a preceding point of the circuit to become admixed with uid products from a preceding polymerization zone, and then passing components of the resultant mixture within approximately the boiling range of the aforesaid charge through the zone next following the last-mentioned polymerization zone, and controlling the aforesaid recycling step so that the ratio of recycled hydrocarbons to the last-mentioned fluid products in the aforesaid 'resultant mixture will be not more than 5 to 1.

'4. Process of treating low boiling, normally gaseous hydrocarbons to produce higher boiling,.

normally liquid products comprising sending a charge of low boiling hydrocarbons containing substantial amounts of unsaturates under reaction conditions through a polymerization zone,

' lsending a portion of the products from said polymerization zone, which boilsapproximately with- Ain the range of the aforesaid charge, under reacproducts from the rst-mentioned polymerization zone, through said subsequent polymerization zone, the ratio of recycled to unrecycled hydrocarbons introduced into said subsequent polymerization zone being within the range of from 0.5:1 up 130,5:1 and polymerization in both zones being effected in liquid phase and at temperatures not exceeding substantially 300 F.

5. Process of treating low boiling, normally gaseous Ihydrocarbons to produce higher boiling', normally liquid products comprising sending a Cil charge of low boiling hydrocarbons containing substantial amounts of unsaturates under reaction conditions and in liquid phase through a polymerization zone, fractionating the products leaving said polymerization zone to remove normally liquid polymers therefrom, sending at least a portion of` the remainder of said products, which boil within the boilingrange of the aforesaid charge, under reaction conditions and in liquid phase through a subsequent polymerization zone, and sending at least a portion of the products from said subsequent polymerization zone into admixture with products from the first-mentioned polymerization zone, prior to fractionation of the last-mentioned products, to undergo further treatment in said subsequentpolymerization zone, the ratio of products recycled from said subsequent polymerization zone to products from said first-mentioned polymerization zone being within the range of 0.5:1 up to 5:1.

6. Process of treating low boiling, normally gaseous hydrocarbons to produce higher boiling, normally liquid products comprising send- 'ing a charge of low boil-ing hydrocarbons rich in unsaturates under predetermined reaction conditions through a polymerization zone to effect j a polymerization of only a portion of said unsaturat'es; fractionating `the productsV leaving said polymerization zone to remove normally liquid polymers therefrom, sending at least a portion u of the remainder of said products, which boil within the boiling range of the aforesaid charge, under'reaction conditions through a subsequent polymerization zone, the reaction conditions for polymerization being more drastic in said subsequent polymerization zone than in the first-mentioned polymerization zone; separating normally liquid polymers from at least a portion of the products from said subsequent polymerization zone, and sending at least a portion of the remainder of the last-mentioned products, which boil within the boiling range of the aforesaid charge, in admixture with the aforesaid portion of the products from the mst-mentioned polymerization zone through said subsequent'polymerizing zone and in the ratio of recycled to unrecycled products of about 2:1, polymerization being effected in both said zones in liquid phase by the action of catalysts comprising silica and alumina in controlled ratio.

EUGENE J. HOUDRY. 

